NOvA collaboration celebrates in northern Minnesota

The University of Minnesota and the NOvA collaboration celebrate the experiment's new far detector with cake. From left: NOvA Laboratory Director Marvin Marshak, University of Minnesota Regents Chair Richard Beeson and University of Minnesota Regent Clyde Allen. Photo: William Miller, NOvA far detector supervisor

In 2012, upon beholding the newly completed NOvA far-detector building in northern Minnesota, the University of Minnesota's Marvin Marshak didn't believe the collaboration would be able to adequately populate it. At the time, the mammoth structure, which is the length of two basketball courts and would house the future NOvA detector, impressed visitors with the full force of not only its size, but its emptiness.

"It was scary. We looked at this building and thought, 'Are we really going to be able to fill this place up?'" said Marshak, NOvA laboratory director. "People looked like tiny little insects against the backdrop of the building."

His worries were needless. On Thursday, the NOvA collaboration celebrated the new detector, which now fills the building nicely, in Ash River, Minnesota.

The celebration came near the conclusion of NOvA's collaboration meeting, which took place in Minneapolis. Attendees took a one-day excursion to the far detector, 280 miles north, to see the detector.

The collaboration also discussed the beginning of data taking with the full detectors in the next few weeks. A celebration at Fermilab is planned for later this year.

NOvA, a Fermilab-hosted neutrino experiment, makes use of two detectors: a smaller, underground detector at Fermilab and the much larger, 14-kiloton detector in Minnesota. The neutrino beam, originating at Fermilab through the NuMI beamline, travels 500 miles from the near detector through the Earth to the far detector.

NOvA scientists will work to uncover the true mass ordering of neutrinos' three types. They'll also look for evidence of CP violation, which could help explain why there is so much more matter than antimatter in our universe and, thus, why we're here.

"We're going to kick all the physics analyses into high gear and get ready for first publications," said Indiana University's Mark Messier, NOvA co-spokesperson. "We hope to have first results by the end of the year."

It's been a long time coming. Researchers submitted a letter of intent to show their interest in a new neutrino experiment in 2002. In the years since, the collaboration has been hard at work designing, developing, producing and installing hardware, software, fiber optics and even the glue that would hold the kiloton-scale blocks' components together.

With almost all of the modules of the detector already taking data, it's a new era for NOvA and the Fermilab neutrino program.

"We're excited to get this experiment up and running — we've been working toward this for a long time," said Fermilab's Pat Lukens, manager for the far detector assembly.

"For at least the next 10 years, there are only two long-baseline neutrino beam experiments in the world — NOvA and T2K," Marshak said, referring to the Japanese experiment. "Some of the answers we're looking for are going to come from the experiments that we have right now."

—Leah Hesla

Attendees at the NOvA celebration, which took place in Ash River, included, from left: NOvA co-spokesperson Mark Messier of Indiana University, University of Minnesota Regents Chair Richard Beeson, UM Dean of the College of Science and Engineering Steven Crouch, UM Vice President of Research Brian Herman, NOvA Laboratory Director Marvin Marshak, Head of the UM School of Physics and Astronomy Ron Poling and NOvA co-spokesperson Gary Feldman. Other speakers were U.S. Senator Amy Klobuchar (via video), DOE NOvA Project Director Pepin Carolan and Fermilab Neutrino Division Head Gina Rameika. Photo: William Miller, NOvA far detector supervisor

In the News

Had there been no Higgs boson, this observation would have been the bomb

From Science, July 22, 2014

Ever wonder what particle physicists would have done had the Higgs boson not existed? Even before they fired up the atom smasher that 2 years ago blasted out the Higgs — the $5.5 billion Large Hadron Collider (LHC) at the European particle physics lab, CERN, near Geneva, Switzerland — researchers said that if they didn't find that coveted quarry, it wouldn't be a total disaster. If there were no Higgs, they said, then a particular ordinary particle interaction should instead go haywire and hint at whatever nature was doing to get by without the Higgs. Now, physicists at the LHC have spotted the rare interaction in that "no-lose" theorem, which is known as WW scattering.

The Higgs gives mass to matter, too

The Higgs field was recently found to give mass to leptons and quarks (matter particles) as well as the bosons (force particles). Lines in the diagram above indicate interactions between particles: The red lines are new.

Nearly 50 years before its discovery, the Higgs field was proposed as a way to explain why particles have mass. The Standard Model would be internally inconsistent if particles could have mass on their own (that is, as an intrinsic property like charge), but it would not be inconsistent to propose a new field that gives them an effective mass by interacting with them. That new field has come to be known as the Higgs field, and particles of this field are called Higgs bosons.

This story is well known, and it was told in many ways when the Higgs boson was discovered in 2012. What is less well known is that the problem of mass was not a single problem. The reason that force particles (such as W and Z bosons) cannot have intrinsic mass is different from the reason that matter particles (such as electrons and quarks) cannot have intrinsic mass. The effective mass of force particles and matter particles could come from different sources. There could be two Higgs fields, one that only interacts with and gives mass to force particles, the other to matter particles, or perhaps the mechanisms themselves could be completely different.

Many physicists expected that a single Higgs field would pull double duty and give mass to all the particles. This, however, was a hypothesis, based on the expectation that nature is simple and elegant.

As it turns out, nature seems to be simple and elegant. CMS scientists recently published a study of Higgs boson decays to matter particles, complementing its discovery, which was through its decays to force particles. The same Higgs field interacts with both types of particles in the expected way.

Specifically, the study focused on Higgs to tau pairs (tau is a heavy cousin of the electron) and Higgs to b quarks (the b quark is a heavy cousin of the quarks found in the protons and neutrons of an atom). Since this interaction is responsible for mass, it is stronger for more massive particles. Both of these decay products are hard to distinguish from backgrounds, especially the b quarks, so the statistical significance is weak (3.8 sigma, equivalent to a one in 14,000 chance that the combined observation is spurious). However, these decays and all the decays to force particles point back to a single Higgs boson. The basic principles of physics may yet be simple enough to fit on the front of a T-shirt.

—Jim Pivarski

These U.S. graduate students contributed to this analysis.

These U.S. physicists participated in recent test beam studies at Fermilab that will help validate future upgrades to the CMS hadron calorimeter subsystem.